DESCRIPTION:(Adapted from the abstract) The formation of trophectoderm and the differentiation of trophoblasts are critical steps in the establishment and maintenance of pregnancy. Very little is known about the molecular regulation of this differentiation process. The investigator will test his hypothesis in two specific aims. Aim 1. To characterize placental HLH protein DNA and protein protein interactions in vitro and in vivo. Aim 2. To clone trophoblast HLH cDNAs by protein DNA and proteinprotein interactions.